Have read up on regex and still confused.Am i anywhere near correct with the variables?

#!/usr/bin/perl

print("Please enter filename: ");
$filename = <STDIN>;
chomp ($filename);

if ($filename=~m/^[_a-zA-Z][^.]{1,7}\.txt$/)
{
open (READFILE, $filename)|| die "Failed to open $filename: $!";
}
my $filecontents;
{
    local undef $/;
    $filecontents = <READFILE>;
}
close <READFILE>;  #slurps the whole file into variable

my @characters = $filecontents =~ m/./g;   # puts a copy of each match
+ into @characters
my $CharCount = scalar @characters;        # this counts the number of
+ elements in @characters
my @words = $filecontents =~m/\b\s/g;       # number of words
my @paragraph =($                          # number of paragraphs. wha
+t is code for new line char ie carriage return?
my @sentences = $filecontents=~m/\.$/g;    # number of sentences


for (@characters){
    print "$_ \n";
 }                                           # this will print a list 
+of each item counted:



# output data
# open(OUT, ">data1.txt") || die "data1.txt not open: $!";
# close(OUT);
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